Disclaimer: I had a recommendation from a friend, which got me in the door.
The interview process varies based on which team you are talking to. For me the process was fairly straight forward. I was introduced to a team member. After a conversation with him my information was forwarded to the head of the team. Then I was asked to come in for an interview. The interview was casual. I walked through my work, but mostly we just had a conversation about how I, and Ammunition, approach design. After I asked a few questions we wrapped. A few days later I got an offer for a contract position. One month into the contract I was offered a full-time position.